Electrical heating module for air flow heating, in particular for heating and ventilation of seats

ABSTRACT

An electric heating module for heating an air flow, in particular for heating and ventilating seats is provided, having at least one PTC-heating element  8  and at least one heat dissipation area  2  adjacent thereto that allows air to flow therethrough, having heat-conducting ribs  1 , which are in an effective connection to the PTC-heating element  8  and combined therewith to form a module. The heat-conducting ribs  1  are formed from strips, which are combined in the area of the PTC-heating element  8  to form at least one packet of strips  3  formed by ribs  1  being in a heat-conducting contact to one another, while they are fanned out in the heat dissipation area  2.

BACKGROUND

The invention relates to an electrical heating module for heating airflow according to the preamble of claim 1. This heating module isparticularly used for heating and ventilation of seats. It comprisesessentially at least one PTC-heating element and at least one heatdissipation area adjacent thereto having heat-conducting ribs, throughwhich air can flow, effectively connected to the PTC-heating element andcombined with them to form a single module.

PTC-elements are semi-conductor resistors made from ceramics, with theiractive resistance varying depending on temperature. The characteristicresistance-temperature line does not progress linearly: the resistanceof a PTC-heating element initially reduces slightly with an increasingtemperature of the component in order to, then, rise very rapidly at acharacteristic temperature (reference temperature). This overallpositive progression of the characteristic resistance-temperature line(PTC=positive temperature coefficient) leads to a PTC-heating elementhaving self-adjusting features. At a component temperature distinctlylower than the reference temperature the PTC-heating element has a lowerresistance so that appropriately high current can be conducted throughit. When a good heat dissipation from the surface of the PTC-heatingelement is ensured, an appropriately high electric charge is acceptedand released in the form of heat. However, when the temperature of thePTC-heating element exceeds the reference temperature, thePTC-resistance increases rapidly so that the electric power draw islimited to a very low value. The temperature of the component thenapproaches an upper limit, which depends on the heat absorption of theenvironment of the PTC-heating element. Under normal environmentalconditions, the temperature of the component of the PTC-heating elementcan therefore not exceed a characteristic maximum temperature, even whenthe intended heat dissipation is entirely interrupted in a malfunction.This fact and the self-adjusting features of a PTC-heating element,based on which the drawn electric power is precisely equivalent to thethermal power dissipated, predestines PTC-heating elements for the usein heating and/or air conditioning arrangements of vehicles or in otherapplications of air flow heating in vehicles. For safety reasons, inthis application field even in the case of a malfunction no flammabletemperatures may develop in the heating element, although in normaloperation high heating output is required.

In order to heat the interior compartment of motor vehicles it has beenknown to use electric heating modules having a frame, which forms amodule by combining a multitude of PTC-heating elements and adjacentheat dissipating areas, through which air can flow, havingheat-conducting ribs. An example for such electric heating modules knownis found in EP 0 350 528 A1.

In EP b 1 479 918 A1 a complete fan module, comprising a radial fanintegrated in a housing and a heating module of the type mentioned atthe outset, is disclosed serving to heat the seat in a ventilatedvehicle seat. Due to the fact that, for safety reasons, a vehicle seatmay not exceed a maximum temperature at its surface, suitable for humanbeings, heating modules with PTC-heating elements are excellentlysuitable, even in case of a ventilator malfunction, because, while theyprovide the same level of safety, they can release a considerably higherheating power than mats conventionally used in heated seats withelectric resistance wires, whose power draw is very limited for safetyreasons.

The previously known electric modules of the type mentioned at theoutset generally comprise several layers of planar PTC-heating elements,arranged side-by-side, with their narrow sides being in the line of theair flow, with their flat upper sides and their lower sides eachelectrically contacting contact metal sheets. The heat dissipation areasadjacent thereto are provided with meandering metal ribs, which are alsolocated with their narrow sides in line with the air flow and thermallycontact, supported at their broad side, the contacting metal sheets ofthe PTC-heating elements in regular intervals for heat transfer. Inorder to achieve a good heat transfer from the PTC-heating elements tothe heat conducting ribs, a heat conducting glue or other connectiontechniques can be used; however, a more efficient solution has becomewidely accepted, i.e. to insert the PTC-heating elements and the heatconducting bars into a frame, combining them into a module, and toprovide at least one spring element in the frame, which presses thealternating arranged heat dissipation areas with the heat conductingbars and the bars with the PTC-heating elements against one another.

However, this requires a rectangular shape of the electric heatingmodule with cellular structures of the components, which is not the bestchoice with respect to the aerodynamics for heating air, particularlywhen the space for the respective air-flow conducting channels is verylimited, as is the case in motor vehicles. Therefore, it was logical forthe ventilator module for vehicle seats according to EP 1 479 918 A1 touse a radial ventilator. However, it is known that radial ventilatorsare not particularly suitable for this purpose, because they create highpressure with respectively high exiting flow speeds.

Furthermore, an automated production of the known electric heatingmodules is hardly possible due to their multi-layered, spring-loadedstructure within a frame. Rather, a high degree of manual labor isnecessary.

Another example for a ventilator module for motor vehicle seats is foundin EP 1 464 533 A1. U.S. Pat. No. 6,541,757 B1 shows an example for aheating module provided with a blower and resistance heating wires inthe air flow, like in hair dryers, and integrated in a vehicle seat.

SUMMARY

Starting with this prior art, the present invention is based on theobjective of improving an electric heating module of the type mentionedat the outset with regard to automated manufacturing.

This objective is attained by an electric heating module having thefeatures of claim 1. Preferred embodiments and further embodiments ofthe invention are described in claims 2 through 14. A preferred use ofthe heating module according to the invention is found in claim 15.

According to the present invention an electric heating module of thetype mentioned at the outset is modified in that the heat conductingribs are formed from strips, which are connected in the area of thePTC-heating element into at least one packet of strips. This packet ofstrips is formed from bars being in a heat-conducting contact to oneanother, while the strips in the heat dissipation area are fanned outsuch that air can flow through them. The heat transfer from thePTC-heating element into the ribs occurs therefore in an area, in whichthe ribs are combined to a compact packet and act as a massive block, inwhich the heat of the PTC-heating element distributes rapidly. Where theribs extend into the heat dissipation area they are fanned, through,i.e. each being at a distance from one another, by being increasinglyangled at the transfer section to the heat dissipation area towards theedge regions of the packet of strips. Good heat conduction occurs withinthe individual ribs so that the heat in the heat dissipation area can bereleased very efficiently to the air flowing through. Simultaneously,the production of such strips in the form of ribs and combining them topackets of strips as well as the fanning of the ribs in the heatdissipation area allow it to be produced entirely in an automatedfashion and furthermore makes it very efficient and cost effective.

The fanning of the heat conducting ribs formed from strips according tothe invention, starting from the area of the PTC-heating element, inwhich the ribs are combined to packets of strips, naturally causes afan-shaped arrangement of the ribs in the heat dissipation area so thatit has a beneficially curved shape. Particular advantages result fromthe heat dissipation area being embodied accordingly in a circularshape, in particular round, and surround the area of the PTC-heatingelement in a plane positioned approximately perpendicular to the airflow. Thus, in this circular heat dissipation area the ribs extendessentially radially so that the electric heating module according tothe invention can be inserted into a cylindrical, aerodynamicallybeneficial air flow channel or a respective pipe. In this manner, a veryhomogenous flow through the heat dissipation area is ensured withoutforming heat pockets, such as e.g. in the corners of a conventionallyrectangular, cellular arranged heating module. But primarily a heatingmodule with a circular heat dissipation area is suitable for anefficient combination with an axial or diagonal fan; this can beinserted very easily in front or behind the heating module according tothe invention in order to form a ventilating heater safe fromoverheating.

The PTC-heating element can be located between two packets of strips andcontact them not only in a heat-conducting fashion but also electricallyconducting. When simultaneously an electrically insulating frame elementis provided, which is arranged between the two packets of strips andaccepts the PTC-heating element, the PTC-heating element can be suppliedwith power via the packets of strips. This occurs simply in that thefirst packet of strips is located at one side of the PTC-heating elementand connected to the other electrical potential than the other packet ofstrips at the other side of the PTC-heating element so that the currentcan flow through the PTC-heating element necessary for heating it. Inthis way, the PTC-heating element can be integrated in the packet ofstrips in a very compact fashion, in particular assembled therein in anautomated manner, so that respective advantages result with regard to acompact construction, efficient heat transfer, as well as easy automaticmanufacturing.

The electric insulating frame element can not only separate the packetof strips from one another, but can also be embodied in the form of arib and extend into the heat dissipation area. This way it is ensuredthat in the heat dissipation area no unintended electrically conductingbridge can develop between the ribs of one packet of strips and ribs ofthe other packet of strips. Additionally, the frame element can then beprovided with assembly elements for connecting them to a housing for themodule, which again facilitates the automatic machine production.

In this context it must be mentioned that, of course, in a heatingmodule according to the invention three or more packets of strips havingPTC-heating elements positioned therebetween and, if necessary,corresponding electrically insulating frame elements can be combined toa single module as well.

In order to electrically contact the PTC-heating element, contactinglinks can be arranged in or at the packets of strips, which areconnected to the power supply. This also increases the potential levelof automation during the machine production of the heating moduleaccording to the invention.

When an electrically insulating frame element is provided between thepacket of strips, in which the PTC-heating element is integrated it ispreferred for the PTC-heating element to be surrounded by a soft-elasticsealing layer located in the electrically insulating frame element. Thissoft-elastic sealing layer may comprise an O-ring, which againfacilitates the production enormously, or a soft-elastic component ofthe material of the frame element. In the latter case, the frame elementcould be produced, for example, from plastic, using a two-componentinjection technique. In addition to the mechanical protection for thePTC-heating element during the assembly, such a soft-elastic seal alsooffers protection from moisture, which can be rather important for aheating module to be mounted in a seat.

The heat-conducting ribs preferably comprise aluminum or copper sheetmetal strips. Said materials offer high heat conductivity and can beprocessed rather easily in an automated fashion.

The packets of strips, to which the heat-conducting ribs are combined inthe area or the PTC-heating element, are preferably held together bywelding, for example using a laser welding seam or the like.Additionally, the packets of strips can be pressed toward one another bya spring-loaded clamp. This spring-loaded clamp can preferably hold notonly the respective packets of strips but all packets of strips with thePTC-heating element located therebetween and compress them such that theheat exchange between the PTC-heating element and the packets of stripsas well as between the individual ribs is optimized.

For a simple and accurately positioned machine production, the ribsembodied as strips can additionally be provided with centering bores fora correctly positioned stacking during the assembly.

When a housing is provided, into which the electric heating moduleaccording to the invention is integrated, it is preferred for saidhousing to form a cylindrical or, for the purpose of noise reduction, aconical air flow channel, in which the heating module and downstreamand/or upstream in reference to a heating module, an axial or diagonalfan is accepted.

The axial or diagonal fan can be a conventional fan with a fan housingand electric connectors, so that it is useful for the housing of theheating module according to the invention to accept the axial ordiagonal ventilator including its own ventilator housing.

A particular advantage of the electric heating module according to thepresent invention results when it is used as a ventilator in aventilated seat, in particular a vehicle seat, in which the heating ofthe airflow can be switched on, if necessary, to serve as a seat heaterusing the PTC-heating element and the heat conducting ribs.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an embodiment of the present invention is describedand explained in greater detail using the attached drawing. It shows:

FIG. 1 a perspective view of a heating module according to theinvention;

FIG. 2 a top view of the heating module of FIG. 1;

FIG. 3 a perspective exploded view of the heating module of FIG. 1;

FIG. 4 a heating module of FIG. 1 with a housing and fan, prior to theassembly;

FIG. 5 the heating module assembled in the housing in a perspective topview;

FIG. 6 a perspective view of the heating module assembled in thehousing, seen from below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The completely assembled exemplary embodiment of an electric heatingmodule according to the present invention, shown in a perspective viewin FIG. 1, comprises a multitude of heat-conducting ribs 1, made fromaluminum sheet metal strips and radially filling a circular heatdissipation area 2. In the center of the heat dissipation area 2 theheat conducting ribs 1 are combined to a total of four packets of strips3, with the ribs 1 of each packet of strips 3 being closely packed andcontacting one another in a heat conducting and electrically conductingmanner. Using welding seams 4 the ribs 1 of the individual packets ofstrips 3 are fixed to one another.

Two electrically insulating frame elements 5 are arranged between thepackets of strips 3, which insulate the two central packets of strips 3each from the exterior packets of strips 3. The frame elements 5 extendfrom the central area inside the heat dissipation area 2 towards theheat dissipation area 2 and continue towards the assembly elements 6, atwhich a housing and a fan can be attached, as described below.

The two central packets of strips 3 are only separated from one anotherby a contact bar 7, by which the PTC-heating elements (here not shown)integrated in the frame elements 5 can be connected to a power supply(not shown). Additional contact bars 7 are provided at the edge regionof the exterior packet of strips 3 in order to also connect therespective other contact surfaces of the PTC-heating elements to thepower supply.

The electrical contacting is illustrated with charge symbols in FIG. 2,which is a top view of the electrical heating module of FIG. 1. Thecentral contact bar 7, symbolized with a plus sign, is switched toanother electric potential than the two exterior contact bars 7, whichare marked with a minus sign. Due to the fact that the ribs 1 in thecentral area around the two PTC-heating elements located in the frameelements 5 are supported on one another over their entire surface theynot only form a good heat conductor but also a good electric conductorso that the current from the contact bars 7 reach the PTC-heatingelements via the packets of strips 3. The electrically insulating frameelements 5 ensure that no short can develop in the area of the packetsof strips 3 or in the heat release area 2.

In FIG. 3, an exploded view of FIG. 1, it is discernible how the two nowvisible PTC-heating elements 8 are integrated in the frame elements 5.The frame elements 5, additionally provided at the top and the bottomwith assembly frames 9 for an exact positioning, are provided with acircular recess 10, into which the PTC-heating elements 8 and an O-ring11 can be inserted in a form-fitting manner. The heat-conducting ribs 1are combined to packets of strips 3 in their central areas, while theyradially fan out in the heat dissipation area 2. The packets of strips 3are fixed via welding seams 4. The ribs 1 are provided with centralbores 12, by which they can be stacked exactly in order to form thepackets of strips 3. After the assembly of the four packets of strips 3and the two frame elements 5 with the two PTC-heating elements 8 as wellas the assembly therebetween and/or superimposition of the contact bars7 the entire module is finally fixed with the spring-loaded clamp 13. Inaddition, the spring-loaded clamp 13 permanently presses the packets ofstrips 3 towards one another so that the packets of strips 3 positionedat both sides of the PTC-heating elements 8 are pressed against thePTC-heating elements in order to ensure an optimal contact.

Using the FIGS. 1 through 3, it is discernible that the heating moduleaccording to the invention can be very easily assembled, in particularassembled and produced automatically by machines without any problems.As described in the following, the insertion into a housing and theattachment of a fan are also possible very easily just as the electricalcontact of the module via the contacting bar 7.

FIG. 4 shows a perspective view of the electric heating module of FIGS.1 through 3, a housing 14, and an axial fan 15 prior to their assembly.The axial fan 15 comprises a commercial axial fan with a rotor 16, amotor 17, and a housing ring 18. The housing 14 comprises a cylindricalheat exchange area 19, a cylindrical fan area 20, and an air outputopening 21, which is provided with air directing bars 22. A type ofassembly flange 23, having centering pins 24, is formed at the housing14. In order to allow the axial fan 15 to be inserted together with itshousing 18, without having to modify it, the ventilator area 20 isexpanded in reference to the heat exchange area 19, into which theheating module is to be inserted. For this purpose, the assemblyelements 6 of the frame element 5 serve to fix the housing ring 18 ofthe axial fan 15 in the right position in reference to the ribs 1 and tohold them fixed in the housing 14. An opening 25 in the housing servesto guide cables for the power supply of the motor 17 of the axial fan 15as well as to connect the PTC-heating elements via the contact bars 7 tothe power supply.

In the FIGS. 5 and 6, perspective representations of the assembledarrangement of FIG. 4 are shown from the top and the bottom. Using thesedrawings, the present invention shows the compact and easilyautomatically assembled construction of the ventilator with air flowheating, in particular for an assembly into ventilated seats.Simultaneously, using the FIGS. 1 through 6, it is discernible that theheating module according to the invention can be automatically producedand assembled without any problems with a very high degree ofautomation. The housing 14, shown in FIGS. 5 and 6 and provided with anelectric heating module and an axial fan 15, can be used both forventilation, for example of a vehicle seat, or when the PTC-heatingelement is activated, for heating of a seat with a very efficient airflow heating, with the air flow heater being provided withheat-conducting ribs 1 arranged radially, with a circular heatdissipation area 2 producing a very even temperature distribution in thehousing 14, and ultimately in the seat. Due to the particulars of thePTC-heating elements, here a very high initial power is provided forheating, while due to the positive temperature characteristic thePTC-heating elements ensure a tolerable maximum temperature under allcircumstances, i.e. even during malfunctions.

1. An electrical heating module for heating an air flow for heating andventilating seats, comprising at least one PTC-heating element (8) andat least one heat dissipation area (2) adjacent thereto which allows airto flow therethrough, with heat-conducting ribs (1), which are in aneffective connection to the PTC-heating element (8) and are combinedtogether to form a module, the heat-conducting ribs (1) are formed fromstrips, which are combined in an area of the PTC-heating element (8) toform at least one packet of strips (3) formed by the ribs (1) in aheat-conducting contact with one another, and which are fanned out inthe heat dissipation area (2).
 2. An electric heating module accordingto claim 1, wherein the heat dissipation area (2) is generally circularand encircles an area of the PTC-heating element (8) in a plane alignedapproximately perpendicular to the air flow.
 3. An electric heatingmodule according to claim 1, wherein the PTC-heating element (8) islocated between two packets of the strips (3) and contacts them both ina heat-conducting as well as an electrically conducting manner, and anelectrically insulating frame material (5) is arranged between the twopackets of strips (3), into which the PTC-heating element (8) isintegrated, and the PTC-heating element (8) is supplied with power viathe packets of strips (3).
 4. An electric heating element according toclaim 3, wherein the frame element (5) is provided in the form of a rib(1) that extends into the heat dissipation area (2).
 5. An electricheating module according to claim 4, wherein the frame element (5) isprovided with assembly elements (6) for mounting to a housing (14) forthe module.
 6. An electric heating module according to claim 4, whereincontact bars (7) are provided in or at the packets of strips (3) forsupplying power to the PTC-heating elements (8).
 7. An electric heatingmodule according to claim 3, wherein the PTC-heating element (8) issurrounded by a soft-elastic sealing layer located in the electricallyinsulating frame element (5).
 8. An electric heating element accordingto claim 7, wherein the soft-elastic sealing layer is an O-ring (11) ora soft-elastic component of a material which forms the frame element. 9.An electric heating module according to claim 3, wherein the packets ofstrips (3) are held together by a welding seam (4).
 10. An electricheating module according to claim 1, wherein the heat conducting ribs(1) comprise aluminum or copper sheet metal strips.
 11. An electricheating module according to claim 10, wherein the sheet metal strips areprovided with centering bores (12) for a correctly positioned stackingduring assembly.
 12. An electrical heating module according to claim 1,wherein the packets of strips (3) are compressed against one another bya spring-loaded clamp (13).
 13. An electric heating module according toclaim 5, wherein the housing (14) forms a cylindrical or conical airflow channel, in which the heating module and, an axial or diagonal fan(15) is located downstream and/or upstream of the heating module.
 14. Anelectric heating module according to claim 13, wherein the axial ordiagonal fan (15) is positioned in a fan housing (18) of its own, whichis accepted in the housing (14).
 15. An electric heating moduleaccording to claim 1, wherein the heating module is connected to aventilated seat to provide an air flow that can be heated to the seat.16. An electric heating module according to claim 15, wherein the seatis a vehicle seat.